Protective helmets used in contact sports such as hockey may include different types of internal padding to protect the head of the wearer from injury related to impacts. Various standards can be applied to certify such a helmet with respect to impact protection, each having different pass/fail criteria related to the capacity of the helmet to reduce the risk of catastrophic head injury.
As research into the effects of impacts on head injuries progresses, the test standards and related test criteria evolve to reflect such progress. Helmets which may have been certifiable under previous test standards may not qualify for certification on newer tests standards updated in light of such research.